1. Field of the Invention
This invention relates in general to irrigation systems and more particularly to drip, or trickle, irrigation systems with improved emitters.
2. Description of the Prior Art
As is well known in the art, drip or trickle irrigation systems are used to receive water under a relatively high supply line pressure and dispense it to various areas to be irrigated at low pressure and low flow rates. To accomplish this, the relatively high pressure water, usually supplied from a domestic water supply line, or pump, is reduced to an intermediate pressure valve by means of a pressure regulator which is part of the drip irrigation system. The water emerging from the regulator is supplied to a trunk line, or lines, each of which has a plurality of lateral, or branch, lines extending therefrom, and each of the branch lines terminates in an emitter device which is located in an area to be irrigated. The intermediate water pressure valve, i.e. the pressure of the water emerging from the pressure regulator, while lower than the supply line pressure, must be at a value that is high enough to insure that a proper supply and flow of water is provided in the trunk line(s) and the plural branch lines thereof. Therefore, a final pressure drop and controlling of the flow rate is accomplished in the emitters themselves.
In some types of prior art emitters, such as that disclosed in U.S. Pat. No. 3,863,845, the water received from the branch line is passed through a pressure reducing helical path and is emitted through a relatively small orifice to produce the desired drip, or trickle, flow rate. Another form of prior art emitter, as disclosed, for example, in U.S. Pat. No. 3,938,552, includes a pressure reducing vibration element which interacts with a small water outlet orifice to achieve the desired irrigation drip flow rate. In U.S. Pat. No. 4,223,838, a spring-loaded metering plunger cooperates with a small water outlet orifice to achieve the desired flow rate.
As can be appreciated, especially by those familiar with irrigation in arid regions where irrigation is needed most, the water available for irrigation is often contaminated with sand and other foreign matter, and often contains chemicals and usually has a high salt content. Such water can, and often does, cause problems with the pressure regulator devices of the emitters, and is most troublesome with regard to cloging of the pressure reducing structures and the small outlet orifices with foreign particles and deposited minerals.
As a result, drip, or trickle irrigation systems will usually be provided with relatively fine mesh filters up stream of the emitters and of course, such filters are relatively expensive, must be checked rather frequently and cleaned when necessary, and this is a chore which is often neglected. In some systems, the emitters are provided with cleaning devices, some of which must be manually actuated, and others which are alleged to be self-cleaning.
From the above, it will be seen, that the prior art emitters per se, and indeed, the drip irrigation systems themselves, can be quite complex and costly, and even the most efficient and elaborate systems require continuing surveillance and maintenance.
Therefore, a need exists for a new and improved trickle irrigation system and emitters for use therein, which overcome some of the problems and shortcomings of the prior art.